gif_cond_exp_multisynapse – Conductance-based generalized integrate-and-fire neuron (GIF) with multiple synaptic time constants (from the Gerstner lab)¶
Description¶
gif_cond_exp_multisynapse
is the generalized integrate-and-fire neuron
according to Mensi et al. (2012) [1] and Pozzorini et al. (2015) [2], with
postsynaptic conductances in the form of truncated exponentials.
This model features both an adaptation current and a dynamic threshold for spike-frequency adaptation. The membrane potential (V) is described by the differential equation:
where each \(\eta_i\) is a spike-triggered current (stc), and the neuron model can have arbitrary number of them. Dynamic of each \(\eta_i\) is described by:
and in case of spike emission, its value increased by a constant (which can be positive or negative):
Neuron produces spikes stochastically according to a point process with the firing intensity:
where \(V_T(t)\) is a time-dependent firing threshold:
where \(\gamma_i\) is a kernel of spike-frequency adaptation (sfa), and the neuron model can have arbitrary number of them. Dynamic of each \(\gamma_i\) is described by:
and in case of spike emission, its value increased by a constant (which can be positive or negative):
Note
In the current implementation of the model, the values of \(\eta_i\) and \(\gamma_i\) are affected immediately after spike emission. However, GIF toolbox, which fits the model using experimental data, requires a different set of \(\eta_i\) and \(\gamma_i\). It applies the jump of \(\eta_i\) and \(\gamma_i\) after the refractory period. One can easily convert between \(q_{\eta/\gamma}\) with these two approaches:
The same formula applies for \(q_\gamma\).
On the postsynaptic side, there can be arbitrarily many synaptic time
constants (gif_psc_exp has exactly two: tau_syn_ex
and
tau_syn_in
). This can be reached by specifying separate receptor
ports, each for a different time constant. The port number has to
match the respective receptor_type
in the connectors. The shape of
synaptic conductance is exponential.
When connecting to conductance-based multisynapse models, all synaptic weights must be non-negative.
Parameters¶
The following parameters can be set in the status dictionary.
Membrane Parameters |
||
C_m |
pF |
Capacity of the membrane |
t_ref |
ms |
Duration of refractory period |
V_reset |
mV |
Reset value for V_m after a spike |
E_L |
mV |
Leak reversal potential |
g_L |
nS |
Leak conductance |
I_e |
pA |
Constant external input current |
Spike adaptation and firing intensity parameters |
||
q_stc |
list of nA |
Values added to spike-triggered currents (stc) after each spike emission |
tau_stc |
list of ms |
Time constants of stc variables |
q_sfa |
list of mV |
Values added to spike-frequency adaptation (sfa) after each spike emission |
tau_sfa |
list of ms |
Time constants of sfa variables |
Delta_V |
mV |
Stochasticity level |
lambda_0 |
real |
Stochastic intensity at firing threshold V_T i n 1/s. |
V_T_star |
mV |
Base threshold |
Synaptic parameters |
||
tau_syn |
list of ms |
Time constants of the synaptic conductance (same size as E_rev) |
E_rev |
list of mV |
Reversal potentials (same size as tau_syn) |
Integration parameters |
||
gsl_error_tol |
real |
This parameter controls the admissible error of the GSL integrator. Reduce it if NEST complains about numerical instabilities |
References¶
Sends¶
SpikeEvent
Receives¶
SpikeEvent, CurrentEvent, DataLoggingRequest